why my photos look like crap after I export them using lightroom? But on LR they look fantastic

hey guys, I'm using LR 5.7 and for a while now I've notice that the sharpening (the quality sharpness I mean) that I see on my images inside LR is not being exported to my jpgs. The result is always this crappy version of what I just did unsure emoticon
Can you please help me figure it out what is happening?!?!
I'm trying with no success to find an answer to this question for days
the LR gives me, for the first second on the develop mode, a glance of the crappy version of the img (the final crappy version) and then changes to the fantastic and good version (the never gets exported the way it is)

Usually the issue is that what you're seeing in Develop is oversharpened due to using Fit Zoom. The image is not actually that sharp but the resampling algorithm used to make the image fit on screen isn't very accurate because it is try to be fast.

To properly judge sharpness you should be using 1:1 or 100% zoom.

In the Detail section where you do noise-reduction and sharpening there is a warning icon that when hovered over says to use 1:1 or 100% zoom to best judge the effects of settings in the Detail settings.

What happens if you compare your Develop and Export versions using 1:1 zoom?